Image pickup device and image pickup apparatus

ABSTRACT

An image pickup device according to the present disclosure includes a first pixel and a second pixel each including a photodetection section and a light condensing section, the photodetection section including a photoelectric conversion element, the light condensing section condensing incident light toward the photodetection section, the first pixel and the second pixel being adjacent to each other and each having a step part on a photodetection surface of the photodetection section, in which at least a part of a wall surface of the step part is covered with a first light shielding section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/234,821, filed Aug. 11, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/778,738, filed Sep. 21, 2015, now U.S. Pat. No.9,450,005, which claims priority to PCT Application No.PCT/JP2014/059018 having an international filing date of Mar. 27, 2014,which designated the United States, which PCT application claimed thebenefit of Japanese Patent Application No. 2013-073054 filed Mar. 29,2013, and Japanese Patent Application No. 2014-049049 filed Mar. 12,2014, the disclosures of which are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present technology relates to an image pickup device and an imagepickup apparatus. More specifically, the present technology relates toan image pickup device having a focus detection function and to an imagepickup apparatus including the image pickup device.

BACKGROUND ART

In recent years, a semiconductor imaging apparatus (an image pickupapparatus) including an image pickup device (a solid-state image pickupdevice) that has a focus detection function of phase differencedetection system has been used. In the phase difference detectionsystem, focus detection of pupil division system is used with use oftwo-dimensional sensor in which on-chip lens is provided in each pixelof the sensor.

In such an image pickup apparatus, technology meeting photodetectioncharacteristics necessary for a pixel for image pick-up (an image pickuppixel) and a pixel for focus detection (an image plane phase differencepixel) has been developed. For example, in PTL 1, there is disclosed animage pickup apparatus in which an element isolation layer formed of anon-transparent conductive material is provided on a back surface of asilicon substrate on a light incident side to improve both of pupildivision property and sensitivity.

Moreover, for example, in PTL 2, there is disclosed an image pickupapparatus in which a height of an on-chip lens is varied for each of animage pickup pixel and an focus detection pixel to adjust a lightcondensing position in each pixel.

Further, for example, in PTL 3, there is disclosed an image pickupapparatus in which a light waveguide is provided between a photoelectricconversion section and an on-chip lens of an image pickup pixel to meetphotodetection characteristics necessary for the image pickup pixel anda focus detection pixel with the same lens shape.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2012-84816

PTL 2: Japanese Unexamined Patent Application Publication No.2007-281296

PTL 3: Japanese Unexamined Patent Application Publication No. 2011-29932

SUMMARY OF INVENTION

However, in a case where the shape of the on-chip lens is changed foreach of the image pickup pixel and the focus detection pixel or in acase where an element isolation layer or a light waveguide is provided,cost and the number of manufacturing steps may be increased. Moreover,in a backside irradiation type image pickup apparatus detecting light bybackside of a silicon substrate, in particular, a member on thephotodetection side may be preferably formed with a small thickness(reduced in height) in order to suppress color mixing. In this case,however, the light condensing position of the incident light is locatedon the silicon substrate side. Therefore, sufficient autofocuscharacteristics (AF characteristics) in the focus detection pixel arenot obtainable.

Therefore, it is desirable to provide an image pickup device and animage pickup apparatus that are adapted to achieve both of pixelcharacteristics of an image pickup pixel and AF characteristics of animage plane phase difference pixel with simple structure.

An image pickup device according to an embodiment of the technologyincludes a first pixel and a second pixel each including aphotodetection section and a light condensing section, thephotodetection section including a photoelectric conversion element, thelight condensing section condensing incident light toward thephotodetection section, the first pixel and the second pixel beingadjacent to each other and each having a step part on a photodetectionsurface of the photodetection section. At least a part of a wall surfaceof the step part is covered with a first light shielding section.

The light condensing section may include a lens as an optical functionallayer, and the lens of the light condensing section of the first pixelmay have a same shape as the lens of the light condensing section of thesecond pixel.

The lens of the light condensing section of the first pixel may beopposed to the photodetection section of the first pixel, and the lensof the light condensing section of the second pixel may be opposed tothe photodetection section of the second pixel.

The wall surface of the step part may be perpendicular.

The second pixel may include a second light shielding section thatshields a part of the photodetection surface, between the photodetectionsection and the light condensing section.

The first pixel and the second pixel may include a third light shieldingsection between the first pixel and the second pixel adjacent to eachother.

The first light shielding section, the second light shielding section,and the third light shielding section may be formed of a same material.

The incident light of the first pixel may be condensed near thephotodetection surface of the photodetection section.

The incident light of the second pixel may be condensed at a depthposition same as a depth position of the second light shielding section.

The step part may be filled with an organic film.

The organic film may be formed of one of a polyimide resin, an acrylicresin, a styrene resin, and an epoxy resin.

The first pixel and the second pixel each may include a fixed chargefilm between the photodetection section and the light condensingsection.

The first pixel and the second pixel may include a groove between thefirst pixel and the second pixel adjacent to each other, and the fixedcharge film may be provided along wall surfaces and a bottom surface ofthe groove.

The groove may be filled with an insulating material.

The groove may be filled with an insulating material and one of thefirst light shielding section, the second light shielding section, andthe third light shielding section.

A drive section including a wiring layer may be provided between thelight condensing section and the photodetection section, and the wiringlayer may also serve as the first light shielding section, the secondlight shielding section, and the third light shielding section.

The light condensing section may include a color filter of red, green,blue, or while, and the light condensing section of the second pixel mayinclude a color filter of green or while.

An inner lens may be provided on the step part.

The inner lens may be an inner lens having an upward convex structure ora downward convex structure, or a rectangular inner lens.

An image pickup apparatus according to an embodiment of the technologyincludes an image pickup device. The image pickup device includes afirst pixel and a second pixel each including a photodetection sectionand a light condensing section, the photodetection section including aphotoelectric conversion element, the light condensing sectioncondensing incident light toward the photodetection section, the firstpixel and the second pixel being adjacent to each other and each havinga step part on a photodetection surface of the photodetection section.At least a part of a wall surface of the step part is covered with afirst light shielding section.

The image pickup device according to the embodiment of the technologyincludes the first pixel and the second pixel each including aphotodetection section and a light condensing section, thephotodetection section including a photoelectric conversion element, thelight condensing section condensing incident light toward thephotodetection section, the first pixel and the second pixel beingadjacent to each other and each having a step part on a photodetectionsurface of the photodetection section, in which at least a part of awall surface of the step part is covered with a first light shieldingsection.

In the image pickup apparatus according to the embodiment of thetechnology, the above-described image pickup device according to theembodiment of the technology is provided.

According to the embodiment of the technology, it is possible tocondense the incident light at a position suitable for each of the imagepickup pixel and the image plane phase difference pixel while reducingoblique incident light from an adjacent pixel. Further, it is possibleto achieve both of the pixel characteristics of the image pickup pixeland the AF characteristics of the image plane phase difference pixelwith simple structure.

Note that effects described here are non-limiting. Effects achieved bythe technology may be one or more of effects described in the presentdisclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional diagram illustrating an example of an image sensoraccording to a first embodiment of the disclosure.

FIG. 2 is a plan view of the image sensor illustrated in FIG. 1.

FIG. 3 is a sectional diagram illustrating a detailed structure of theimage sensor illustrated in FIG. 1.

FIG. 4 is a plan view illustrating another arrangement structure of theimage sensor according to the first embodiment of the disclosure.

FIG. 5 is a sectional diagram of the image sensor illustrated in FIG. 4.

FIG. 6 is a block diagram illustrating a peripheral circuitconfiguration of a photodetection section illustrated in FIG. 1.

FIG. 7A is a sectional schematic diagram illustrating an image sensorand incident light as a comparative example.

FIG. 7B is a characteristic diagram illustrating relationship between anincident angle and photodetection efficiency in the image sensorillustrated in FIG. 7A.

FIG. 8A is a sectional schematic diagram illustrating the image sensorillustrated in FIG. 1 and incident light.

FIG. 8B is a characteristic diagram illustrating relationship between anincident angle and photodetection efficiency in the image sensorillustrated in FIG. 8A.

FIG. 9 is a sectional diagram of an image sensor according to amodification 1.

FIG. 10 is a sectional diagram of an image sensor according to amodification 2.

FIG. 11 is a sectional diagram illustrating an example of an imagesensor according to a second embodiment of the disclosure.

FIG. 12 is a sectional diagram illustrating another example of the imagesensor according to the second embodiment of the disclosure.

FIG. 13 is a sectional diagram illustrating still another example of theimage sensor according to the second embodiment of the disclosure.

FIG. 14 is a sectional diagram illustrating an example of an imagesensor according to a third embodiment of the disclosure.

FIG. 15 is a sectional diagram illustrating an example of the imagesensor according to the third embodiment of the disclosure.

FIG. 16 is a sectional diagram illustrating an example of the imagesensor according to the third embodiment of the disclosure.

FIG. 17 is a sectional diagram illustrating an example of the imagesensor according to the third embodiment of the disclosure.

FIG. 18 is a sectional diagram illustrating an example of the imagesensor according to the third embodiment of the disclosure.

FIG. 19 is a diagram for explaining manufacture of the image sensoraccording to the third embodiment of the disclosure.

FIG. 20 is a diagram for explaining the manufacture of the image sensoraccording to the third embodiment of the disclosure.

FIG. 21 is a diagram for explaining the manufacture of the image sensoraccording to the third embodiment of the disclosure.

FIG. 22 is a functional block diagram illustrating an entireconfiguration according to an application example 1 (an image pickupapparatus).

FIG. 23 is a functional block diagram illustrating an entireconfiguration according to an application example 2 (a capsule endoscopecamera).

FIG. 24 is a functional block diagram illustrating an entireconfiguration according to another example of the endoscope camera (aninsertion endoscope camera).

FIG. 25 is a functional block diagram illustrating an entireconfiguration according to an application example 3 (a vision chip).

DESCRIPTION OF EMBODIMENTS

Hereinafter, some embodiments of the disclosure will be described indetail with reference to drawings. Note that description will be givenin the following order.

-   1. First embodiment (a backside irradiation type image sensor; an    example in which a step part is provided between a first pixel and a    second pixel, and a first light shielding section is provided on a    side wall of the step part)-   2. Modification 1 (an example in which a groove is provided between    pixels and the groove is filled with an insulating material)-   3. Modification 2 (an example in which a groove is provided between    pixels and the groove is filled with an insulating material and a    light shielding section)-   4. Second embodiment (a surface irradiation type image sensor; an    example in which a first light shielding section is formed of a    wiring layer)-   5. Third embodiment (a backside irradiation type image sensor; an    example in which a step part is provided between a first pixel and a    second pixel, a first light shielding section is provided on a side    wall of the step part, and an inner lens is further provided)-   6. Application examples (application examples of electronic    apparatuses)

1. First Embodiment

FIG. 1 illustrates a sectional structure of an image sensor (an imagesensor 1A) according to a first embodiment of the disclosure. The imagesensor 1A may be, for example, a backside irradiation type (a backsurface photodetection type) solid-state image pickup device (chargecoupled device (CCD) image sensor, complementary metal-oxidesemiconductor (CMOS)), and a plurality of pixels 2 are two-dimensionallyarranged on a substrate 21 (see FIG. 3).

Note that FIG. 1 illustrates a sectional structure of the image sensoralong I-I line illustrated in FIG. 2. The pixels 2 includes image pickuppixels 2A (first pixels) and image plane phase difference pixels 2B(second pixels). In the present embodiment, a step part 20A is providedon photodetection surfaces 20S between the image pickup pixel 2A and theimage plane phase difference pixel 2B that are adjacent to each other,and a side wall 20B of the step part 20A is covered with a lightshielding film 14A (a first light shielding film).

FIG. 3 illustrates a detailed sectional structure of the pixels 2 (theimage pickup pixels 2A and the image plane phase difference pixels 2B).Each of the image pickup pixels 2A and the image plane phase differencepixels 2B includes a photodetection section 20 including a photoelectricconversion element (a photodiode 23) and a light condensing section 10condensing incident light toward the photodetection section 20. Each ofthe image pickup pixels 2A photoelectrically converts an object imageformed by an image pickup lens by the photodiode 23 to generate a signalfor image generation.

Each of the image plane phase difference pixels 2B divides a pupilregion of an image pickup lens, and photoelectrically converts theobject image from the divided pupil region to generate a signal forphase difference detection. The image plane phase difference pixels 2Bare discretely disposed between the image pickup pixels 2A asillustrated in FIG. 2. Note that the image plane phase difference pixels2B are not necessarily disposed independently as illustrated in FIG. 2,and for example, may be disposed in line as with P1 to P7 in a pixelsection 200 as illustrated in FIG. 4. FIG. 5 illustrates a sectionalstructure of the image sensor 1B in which a plurality of image planephase difference pixels 2B are arranged in line, taken along II-II lineillustrated in FIG. 4.

As described above, in the present embodiment, the step part 20A isprovided on the photodetection surface 20S of the photodetection section20 between the image pickup pixel 2A and the image plane phasedifference pixel 2B that are disposed adjacently to each other. In otherwords, the photodetection surface 20S of the image plane phasedifference pixel 2B is formed at a position lower by one level than theposition of the image pickup pixel 2A, with respect to an emissionsurface 11S of an on-chip lens 11. A height h of the step part 20A maybe preferably, for example, 0.05 μm or larger and 2 μm or lower, andmore preferably 0.3 μm or larger and 1 μm or lower, depending oncurvature etc. of the on-chip lens 11.

The side wall 20B of the step part 20A is covered with a light shieldingfilm 14 (the light shielding film 14A) in order to prevent crosstalk ofoblique incident light between the image pickup pixel 2A and the imageplane phase difference pixel 2B that are adjacent to each other. Notethat the light shielding film 14A may be preferably provided over theentire surface of the side wall 20B of the step part 20A; however, thelight shielding film 14A may cover at least a part of the side wall 20Bto reduce the crosstalk of oblique incident light.

(Light Condensing Section 10)

The light condensing section 10 is provided on the photodetectionsurface 20S of the photodetection section 20, and has the on-chip lens11 that is disposed oppositely to each pixel 2, on the light incidentside as an optical functional layer. In the light condensing section 10,a color filter 12, a planarizing film 13, and the light shielding film14 are provided between the on-chip lens 11 and the photodetectionsection 20 in order from the on-chip lens 11. In addition, an insulatingfilm 15 is provided on the photodetection section 20 side of theplanarizing film 13 and the light shielding film 14.

The on-chip lens 11 has a function of condensing light toward thephotodetection section 20 (specifically, the photodiode 23 of thephotodetection section 20). A lens diameter of the on-chip lens 11 isset to a value corresponding to the size of the pixel 2, and forexample, may be 0.9 μm or larger and 3 μm or lower. Moreover, arefractive index of the on-chip lens 11 may be, for example, 1.1 to 1.8.The lens may be formed using, for example, an organic resin material.

In the present embodiment, the on-chip lens 11 provided on the imagepickup pixel 2A has the same shape as the on-chip lens 11 provided onthe image plane phase difference pixel 2B. Here, the same means that theon-chip lens 11 is manufactured using the same material through the samesteps, which does not eliminate variation caused by various conditionsin manufacturing.

The color filter 12 may be, for example, any of a red (R) filter, agreen (G) filter, a blue (B) filter, and a white (W) filter, and may beprovided, for example, for each pixel 2. These color filters 12 areprovided in a regular color arrangement (for example, Bayerarrangement). Providing such color filters 12 makes it possible toobtain photodetection data of colors corresponding to the colorarrangement in the image sensor 1.

Note that the color arrangement of the color filters 12 in the imageplane phase difference pixel 2B is not particularly limited; however,the green (G) filter or the white (W) filter may be preferably used inorder to use autofocus (AF) function even in a dark place with a smallquantity of light. Incidentally, in a case where the green (G) filter orthe white (W) filter is assigned to the image plane phase differencepixel 2B, the photodiode 23 of the image plane phase difference pixel 2Bis easily saturated in a bright place with a large quantity of light. Inthis case, an overflow barrier of the photodetection section 20 may beclosed.

The planarizing film 13 is charged in a recess formed by the step part20A and planarizes the photodetection surface 20S of the photodetectionsection 20. As the material of the planarizing film 13, an inorganicmaterial and an organic material may be used. Examples of the inorganicmaterial may include an insulating film material, specifically, asilicon oxide film (SiO₂), a silicon nitride film (SiN), and a siliconoxynitride film (SiON).

Examples of the organic material may include a polyimide resin, anacrylic resin, a styrene resin, and an epoxy resin. The planarizing film13 is formed of a single layer film or a stacked-layer film formed ofany of the material described above. A thickness of the planarizing film13 (a film thickness of the planarizing film 13 in the image pickuppixel 2A) may be preferably, for example, 50 μm or larger and 500 μm.Note that the organic film made of the organic material has highadhesiveness. Therefore, when the planarizing film 13 has astacked-layer structure of the inorganic film and the organic film, itis possible to suppress occurrence of peeling of the color filter 12 andthe on-chip lens 11 by providing the organic film on the color filter 12side.

The light shielding film 14 includes a light shielding film 14B (asecond light shielding film) for pupil division in the image plane phasedifference pixel 2B and a light shielding film 14C (a third lightshielding film) provided between the pixels adjacent to each other, inaddition to the light shielding film 14A covering the side wall 20B ofthe step part 20A as described above.

The light shielding film 14 (in particular, the light shielding films14A and 14C) suppresses color mixing caused by crosstalk of obliqueincident light between the pixels adjacent to each other, and isprovided in a lattice shape surrounding each pixel 2 as illustrated inFIG. 2. In other words, the light shielding film 14 has a structure inwhich an opening 14 a is provided on an optical path of the on-chip lens11.

Note that the opening 14 a of the image plane phase difference pixel 2Bis provided at a position (an eccentric position) close to one side of aphotodetection region R of the pixel 2 described later. The lightshielding film 14 may be formed of, for example, tungsten (W), aluminum(Al), or an alloy of Al and copper (Cu), and may have a thickness of,for example, 100 nm or larger and 800 nm.

Note that the light shielding film 14 may be formed by, for example,sputtering. The light shielding film 14C provided between the imagepickup pixel 2A and the image plane phase difference pixel 2B that areadjacent to each other, the light shielding film 14A provided on theside wall 20B of the step part 20A, and the light shielding film 14B forpupil division may be continuously formed of the same material at thesame step.

The insulating film 15 prevents damage of the Si substrate 21 inprocessing of the light shielding film 14, and is provided along theshape of the photodetection section 20. Examples of the material of theinsulating film 15 may include a silicon oxide film (SiO₂), a siliconnitride film (SiN), and a silicon oxynitride film (SiON). A thickness ofthe insulating film 15 may be, for example, 10 nm or larger and 1000 nmor lower.

(Photodetection Section 20)

The photodetection section 20 includes a wiring layer 22, the photodiode23, and a fixed charge film 24. The wiring layer 22 is provided on afront surface (on a side opposite to the photodetection surface 20S) ofthe silicon (Si) substrate 21 and includes transistors and metalwirings, the photodiode 23 is buried in the Si substrate 21, and thefixed charge film 24 provided on the back surface (on the photodetectionsurface side) of the Si substrate 21. A p-type impurity may be formed ona back interface of the Si substrate 21 by ion injection and pinning maybe performed. Alternatively, a negative fixed charge film 24 may beformed to form an inversion layer (not illustrated) near the backsurface of the Si substrate 21.

The photodiode 23 may be a pn-junction type photodiode that may beformed of, for example, an n-type semiconductor region formed in athickness direction of the Si substrate 21 and a p-type semiconductorregion provided near the front surface and the back surface of the Sisubstrate 21. In the present embodiment, the n-type semiconductor regionconfiguring the photodiode 23 is referred to as the photoelectricconversion region R.

Note that the p-type semiconductor region facing the front surface andthe back surface of the Si substrate 21 serves also as a hole chargeaccumulation region for suppressing dark current. In addition, the Sisubstrate 21 also has the p-type semiconductor region between the pixels2, and the pixels 2 are separated from one another by the p-typesemiconductor region.

Incidentally, when a green (G) filter or a white (W) filter is used asthe color filter 12 of the image plane phase difference pixel 2B, thephotodiode 23 is easily saturated. In this case, impurity concentration(here, concentration of p-type impurity) of overflow pass may beincreased to close potential barrier so that the saturation isincreased.

The fixed charge film 24 is provided between the light condensingsection 10 (specifically, the insulating film 15) and the Si substrate21 to fix the charge on the interface between the light condensingsection 10 and the photodetection section 20. As the material of thefixed charge film 24, a high refractive index material having negativecharge may be used, and examples thereof may include hafnium oxide(HfO₂), aluminum oxide (Al₂O₃), zirconium oxide (ZrO₂) film, tantalumoxide (Ta₂O₅), and titanium oxide (TiO₂).

Examples of the method of forming the fixed charge film 24 may includechemical vapor deposition method (hereinafter, referred to as CVDmethod), sputtering method, and atomic layer deposition method(hereinafter, referred to as ALD method). The interface state is reducedby the ALD method during film formation.

It is possible to form the SiO₂ film to have a thickness of about 1 nmat a time. Examples of the material other than those described above mayinclude lanthanum oxide (La₂O₃), praseodymium oxide (Pr₂O₃), ceriumoxide (CeO₂), neodymium oxide (Nd₂O₃), and promethium oxide (Pm₂O₃).Further, examples of the above-described material may include samariumoxide (Sm₂O₃), europium oxide (Eu₂O₃), gadolinium oxide (Gd₂O₃), terbiumoxide (Tb₂O₃), and dysprosium oxide (Dy₂O₃).

In addition, holmium oxide (Ho₂O₃), thulium oxide (Tm₂O₃), ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃) may beused. Note that the film having the negative fixed charge (the fixedcharge film 24) in the present embodiment may be formed of a hafniumnitride film, an aluminum nitride film, hafnium oxynitride film, or analuminum oxynitride film. The film thickness thereof may be, forexample, 4 nm or larger and 100 nm or lower.

FIG. 6 is a functional block diagram illustrating a configuration ofperipheral circuits of the pixel section 200 of the photodetectionsection 20. The photodetection section 20 includes a vertical (V)selection circuit 206, the sample/hold (S/H)-correlated double sampling(CDS) circuit 207, a horizontal (H) selection circuit 208, a timinggenerator (TG) 209, an automatic gain control (AGC) circuit 210, an A/Dconversion circuit 211, and a digital amplifier 212, and these aremounted on the same Si substrate (chip) 21.

Such an image sensor 1A (and 1B) may be manufactured in the followingmanner.

(Manufacturing Method)

First, for example, a conductive impurity semiconductor layer may beprovided by ion injection to the Si substrate 21, and the photodiode 23is formed. Subsequently, after the multilayer wiring layer 22 is formedon the front surface of the Si substrate 21, the Si substrate 21 ispolished to form the photodetection surface 20S. Then, the step part 20Amay be formed at a predetermined position in the region (the pixelsection 200) where the pixel 2 is to be formed on the back surface (thephotodetection surface 20S) of the Si substrate 21, with use of, forexample, dry etching. Here, the side wall 20B of the step part 20A isformed perpendicular to the plane direction of the Si substrate 21;however, the side wall 20B is not necessarily perpendicular to the planedirection of the Si substrate 21. Alternatively, for example, the sidewall 20B of the step part 20A may be inclined as with the case where thestep part 20A is formed with use of wet etching.

Next, the wiring layer 22 having the multilayer wiring structure isformed on a surface (the front surface) on a side opposite to thephotodetection surface 20S of the Si substrate 21. Subsequently, theHfO₂ film may be formed to have a thickness of, for example, 60 nm onthe back surface of the Si substrate 21 by, for example, sputteringmethod to form the fixed charge film 24.

Subsequently, for example, the insulating film 15 by the CVD method andthe light shielding film 14 by the sputtering method may be formed inorder on the fixed charge film 24. Next, the recess of the step part 20Ais filled with the planarizing film 13 and the photodetection section 20is planarized by the planarizing film 13, and then for example, thecolor filter 12 in Bayer arrangement and the on-chip lens 11 are formedin order. In this way, the image sensor 1A is manufactured.

(Action and Effects)

In the image sensor 1A (or 1B) of the backside irradiation type in thepresent embodiment, the thickness of the stacked-layer film (forexample, the color filter 12 and the planarizing film 13) on the lightincident side (the light condensing section 10) may be preferablyreduced in order to suppress occurrence of color mixing between thepixels adjacent to each other. In addition, the highest pixelcharacteristics are obtainable by adjusting a focal point of theincident light on the photodiode 23 in the image pickup pixel 2A,whereas the highest AF characteristics are obtainable by adjusting thefocal point of the incident light on the light shielding film 14B forpupil division in the image plane phase difference pixel 2B.

FIG. 7A schematically illustrates a sectional surface structure of animage sensor 100 as a comparative example of the disclosure and incidentlight entering a pixel 102 configuring the image sensor 100. In theimage sensor 100, a stacked-layer film (a color filter 112 and aplanarizing film 113) of a light condensing section 110 is reduced inheight, each of the pixels 102 has an on-chip lens 111 of the sameshape, and a photodetection surface 120S of an image pickup pixel 102Aand a photodetection surface 120S of an image plane phase differencepixel 102B are provided on the same plane.

In such an image sensor 100, the position where the light emitted fromthe on-chip lens 111 is condensed is located in deeper position close toan Si substrate 121. Therefore, in the image pickup pixel 102A having awide opening 114 a by a light shielding film 114, luminous fluxes ofsubstantially all of the incident light that have passed through theon-chip lens 111 are applied to a photodiode 123. In contrast, in theimage plane phase difference pixel 102B having an eccentric opening 114a by pupil division, a part of the luminous fluxes is shielded by thelight shielding film 114 and is not applied to the photodiode 123. FIG.7B illustrates incident angle characteristics in the image plane phasedifference pixel 102B.

FIG. 8A schematically illustrates the sectional structure of the imagesensor 1B of the present embodiment and the incident light entering eachof the pixels 2A and 2B. In the image sensor 1A, as described above, thestep part 20A is provided between the image pickup pixel 2A and theimage plane phase difference pixel 2B that are adjacent to each other,and the photodetection surface 20S of the image plane phase differencepixel 2B is provided at a position lower by one level than thephotodetection surface 20S of the image pickup pixel 2A.

Specifically, design is made in such a manner that the incident light inthe image pickup pixel 2A is condensed near the photodetection surface20S and the incident light in the image plane phase difference pixel 2Bis condensed at the same depth position as that of the light shieldingfilm 14B for pupil division. Accordingly, similar to the image pickuppixel 2A, the luminous fluxes of substantially all of the incident lightthat have passed through the on-chip lens 11 are applied to thephotodiode 23 also in the image plane phase difference pixel 2B. FIG. 8Billustrates incident angle characteristics in the image plane phasedifference pixel 2B.

In the incident angle characteristic diagrams illustrated in FIG. 7B andFIG. 8B, a horizontal axis indicates an incident angle, and a verticalaxis indicates photodetection efficiency. Comparing the characteristicdiagram in FIG. 7A with the characteristic diagram in FIG. 8B, thephotodetection efficiency of the image plane phase difference pixel 2Bin which the photodetection surface 20S is provided at the positiondeeper than that of the image pickup pixel 2A is higher than thephotodetection efficiency of the image pickup pixel 2A, namely, thecharacteristics of pupil intensity distribution of the image plane phasedifference pixel 2B are sharper than those of the image pickup pixel 2A.In other words, it is possible for the image plane phase differencepixel 2B of the image sensor 1 in the present embodiment to generate thesignal for phase difference detection with accuracy higher than that ofthe image plane phase difference pixel 102B of the image sensor 100 inthe comparative example, in phase difference detection.

Moreover, in the present embodiment, providing the light shielding film14A on the side wall 20B of the step part 20A suppresses color mixingcaused by crosstalk of the oblique incident light between the pixelsadjacent to each other.

As described above, in the present embodiment, each of the image pickuppixel 2A and the image plan phase difference pixel 2B has the lightcondensing section 10 and the photodetection section 20, the step part20A is provided on the photodetection section 20 between the imagepickup pixel 2A and the image plane phase difference pixel 2B that areadjacent to each other, and the side wall 20B of the step part 20A iscovered with the light shielding film 14A. Accordingly, it is possibleto condense the incident light that have passed through the on-chip lens11 opposed to the photodetection section 20 of each pixel 2 at the depthposition suitable for each of the image pickup pixel 2A and the imageplane phase difference pixel 2B while suppressing crosstalk caused bythe oblique incident light between the pixels 2 adjacent to each other.As a result, it is possible to improve the AF characteristics of theimage plane phase difference pixel 2B while maintaining the pixelcharacteristics of the image pickup pixel 2A. In other words, it becomespossible to provide the image pickup unit in which the characteristicsof both of the image pickup pixel 2A and the image plane phasedifference pixel 2B are achieved with the simple structure.

Hereinafter, modifications (modifications 1 and 2) of theabove-described first embodiment and a second embodiment are described.Like numerals are used to designate substantially like components of theabove-described first embodiment, and the description thereof isappropriately omitted.

2. Modification 1

FIG. 9 illustrates a sectional structure of an image sensor (an imagesensor 1C) according to the modification 1. Similarly to the imagesensor 1A (and 1B) of the above-described first embodiment, the imagesensor 1C is a backside irradiation type solid-state image pickupdevice, and has a structure in which a plurality of pixels 2 aretwo-dimensionally arranged.

The pixels 2 includes the image pickup pixels 2A and the image planephase difference pixels 2B, and the step part 20A is provided on thephotodetection surface 20S of the photodetection section 20 between theimage pickup pixel 2A and the image plane phase difference pixel 2B thatare adjacent to each other, similarly to the above-described embodiment.Incidentally, the image sensor 1C according to the present modificationis different from the first embodiment in that a groove 21A is providedbetween the pixels 2 adjacent to each other on the photodetectionsurface 20S side of the photodetection section 20, irrespective of theimage pickup pixel 2A and the image plane phase difference pixel 2B.

The groove 21A provided in the photodetection section 20 of the presentmodification separates the pixels 2 on the photodetection surface 20Sside. The groove 21A is provided in the Si substrate 21 of thephotodetection section 20, and a depth (D) of the groove 21 A providedbetween the image plane phase difference pixels 2B adjacent to eachother may be, for example, 0.1 μm or larger and 5 μm or lower. The fixedcharge film 24 formed continuously from the surface of the Si substrate21 is provided on wall surfaces and a bottom surface of the groove 21A.In addition, the groove 21A covered with the fixed charge film 24 isfilled with the insulating film 15.

In this way, in the present modification, the groove 21A is providedbetween the pixels 2, and the groove 21A is filled with the fixed chargefilm 24 and the insulating material forming the insulating film 15.Therefore, it is possible to further reduce color mixing caused bycrosstalk of the oblique incident light between the pixels adjacent toeach other. Also, an effect of preventing overflow of charge to thephotodiode 23 of the adjacent pixel caused by saturation is exhibited.

3. Modification 2

FIG. 10 illustrates a sectional structure of an image sensor (an imagesensor 1D) according to the modification 2. Similar to theabove-described image sensors 1A to 1C, the image sensor 1D is abackside irradiation type solid-state image pickup device, and has astructure in which a plurality of pixels 2 are two-dimensionallyarranged. The image sensor 1D in the present modification has the groove21A between the pixels 2 adjacent to each other on the photodetectionsurface 20S side of the photodetection section 20, irrespective of theimage pickup pixel 2A and the image plane phase difference pixel 2B,similarly to the image sensor 1C of the modification 1. However, theimage sensor 1D is different from the image sensor of the modification 1in that the groove 21A is filled with the light shielding film 14 inaddition to the fixed charge film 24 and the insulating film 15.

Specifically, in the groove 21A of the present modification, the fixedcharge film 24 and the insulating film 15 provided on the Si substrate21 are continuously provided along the wall surfaces and the bottomsurface of the groove 21A. The groove 21A covered with the fixed chargefilm 24 and the insulating film 15 is filled with the light shieldingfilm 14 provided between the pixels 2 (specifically, the light shieldingfilm 14C between the image pickup pixels (2A and 2A) adjacent to eachother, the light shielding film 14A between the image pickup pixel andthe image plane phase difference pixel (2A and SB), and the lightshielding film 14B between the image plane phase difference pixels (2Band 2B)).

In this way, in the present modification, the groove 21A providedbetween the pixels 2 is filled with the light shielding film 14 inaddition to the fixed charge film 24 and the insulating film 15.Accordingly, it is possible to further reduce crosstalk of the obliqueincident light between the pixels adjacent to each other, as comparedwith the above-described modification 1.

4. Second Embodiment

FIG. 11 illustrates an example of a sectional structure of an imagesensor (an image sensor 1E) according to the second embodiment of thedisclosure. The image sensor 1E may be, for example, a surfaceirradiation type (a front surface photodetection type) solid-state imagepickup device, and has a plurality of pixels 2 two-dimensionallyarranged.

The pixels 2 include the image pickup pixels 2A and the image planephase difference pixels 2B, and the step part 20A is provided on thephotodetection surface 20S between the image pickup pixel 2A and theimage plane phase difference pixel 2B adjacent to each other, similarlyto the first embodiment and the modifications 1 and 2 described above.Incidentally, since the image sensor 1E of the present embodiment is ofthe surface irradiation type, the wiring layer 22 is provided betweenthe light condensing section 10 and the Si substrate 21 configuring thephotodetection section 20, and a metallic film 22B configuring thewiring layer 22 also serves as the light shielding film 14 in the firstembodiment and the like.

In the present embodiment, as described above, the wiring layer 22 thatis provided on a surface opposite to the surface provided with the lightcondensing section 10 of the Si substrate 21 in the first embodiment isprovided between the light condensing section 10 and the Si substrate21, and the metallic film 22B configuring the wiring layer 22 is used asthe light shielding film 14.

Therefore, the light shielding film 14 and the insulating film 15described in the first embodiment and the like are omitted, and thelight condensing section 10 in the present embodiment is configured ofthe on-chip lens 11 and the color filter 12. Further, the fixed chargefilm 24 is also omitted. Similarly to the image sensor 1A and the like,the step part 20A formed on the photodetection section 20 is provided onthe light condensing section 10 side of the Si substrate 21 having thephotodiode 23, and a front surface of the Si substrate 21 provided withthe step part 20A serves as the photodetection surface 20S.

The wiring layer 22 is provided between the light condensing section 10and the Si substrate 21, and has a multilayer wiring structure in which,for example, the metallic film 22B is configured of two layers (22B₁ and22B₂, in FIG. 11) or three or more layers (22B₁, 22B₂, 22B₃, . . . )with an interlayer insulating film 22A in between. The metallic film 22Bis a metallic wiring for the transistors and the peripheral circuits. Inthe typical surface irradiation type image sensor, the metallic film 22Bis provided between the pixels so as to secure an aperture ratio of thepixels and so as not to shield luminous flux emitted from an opticalfunctional layer of the on-chip lens or the like. In the presentembodiment, the metallic film 22B1 provided at a position closest to theSi substrate 21 of the multilayer wiring (the metallic film 22) is usedas the light shielding film 14.

The interlayer insulating film 22A is provided between the metallic film22B₁ and the metallic film 22B₂ (22A₂), between the Si substrate 21 andthe metallic film 22B1 (22A₁), and between the metallic film 22B2 andthe light condensing section 10 (specifically, the color filter 12)(22A₃), and planarizes the recess of the Si substrate 21 formed by thestep part 20A.

As the material of the interlayer insulating film 22A, for example, aninorganic material may be used. Specifically, examples thereof mayinclude a silicon oxide film (SiO), a silicon nitride film (SiN), asilicon oxynitride film (SiON), a hafnium oxide film (HfO), an aluminumoxide film (AlO), an aluminum nitride film (AlN), a tantalum oxide film(TaO), a zirconium oxide film (ZrO), a hafnium oxynitride film, ahafnium silicon oxynitride film, an aluminum oxynitride film, a tantalumoxynitride film, and a zirconium oxynitride film. A thickness of theinterlayer insulating film 22A, specifically, the thickness of theinterlayer insulating film 22A in the image pickup pixel 2A may be, forexample, 100 μm or larger and 1000 μm or lower.

The metallic film 22B (22B₁ and 22B₂) may be an electrode configuring adrive transistor corresponding to each pixel 2, and examples of amaterial of the metallic film 22B may include simple substance of metalelements such as aluminum (Al), chromium (Cr), gold (Au), platinum (Pt),nickel (Ni), copper (Cu), tungsten (W) and silver (Ag), or an alloythereof.

Incidentally, as described above, the metallic film 22B typically has asize suitable for a size between the pixels 2 so as to ensure theaperture ratio of the pixel 2 and so as not to shield the light emittedfrom the optical functional layer of the on-chip lens 11 or the like.Incidentally, in the present embodiment, since the metallic film 22B₁provided on the Si substrate 21 side also serves as the light shieldingfilm 14, the metallic film 22B is formed along the step of theinterlayer insulating film 22A₁ formed by the step part 20A so as tocover a wall surface 22C of the step part, as illustrated in FIG. 11.

As a result, entering of the light that has passed through the on-chiplens 11 of the image pickup pixel 2A to the photodiode 23 of theadjacent image plane phase difference pixel 2B and entering of the lightthat has passed through the on-chip lens 11 of the image plane phasedifference pixel 2B to the photodiode 23 of the adjacent image pickuppixel 2A are suppressed. Further, the metallic film 22B₁ providedbetween the image plane phase difference pixels 2B is expanded to apredetermined position in the photodetection region R of the image planephase difference pixel 2B so as to also serve as the light shieldingfilm 14B for pupil division.

Also, the metallic film 22B₁ provided between the image pickup pixels2A, the metallic film 22B₁ provided between the image pickup pixel 2Aand the image plane phase difference pixel 2B, and the metallic film22B₁ provided on a side where the light shielding film for pupildivision is not formed between the image plane phase difference pixels2B adjacent to each other are each formed in a predetermined size so asto also serve as the light shielding film 14C.

Note that the position where the metallic film 22B₁ as the lightshielding film 14 is formed in the stacking direction of the layers, inparticular, the position where the metallic film B₁ as the lightshielding film 14B between the image plane phase difference pixels 2B isformed may be preferably same as a depth position on which the incidentlight that has passed through the on-chip lens 11 of the image planephase difference pixel 2B is condensed, namely, as the position of thesurface of the Si substrate 21 of the image pickup pixel 2A.

When the formation position of the metallic film 22B₁ on the image planephase difference pixel 2B is higher than the condensing position of theincident light, a part of the luminous fluxes of the incident light isshielded by the metallic film 22B₁, which results in decrease of the AFcharacteristics. The same applies to the case where the formationposition of the metallic film 22B₁ on the image plane phase differencepixel 2B is lower than the condensing position of the incident light.

Such a wiring layer 22 may be formed with use of the followingmanufacturing method, for example. First, for example, a SiO₂ film maybe formed on the Si substrate 21 provided with the step part 20A withuse of, for example, CVD method, and then the interlayer insulating film22A₁ may be formed by etching or polishing. The interlayer insulatingfilm 22A₁ has a step corresponding to the step part 20A provided betweenthe image pickup pixel 2A and the image plane phase difference pixel 2B,and a height of the SiO₂ film on the image plane phase difference pixel2B is substantially equal to a height of the Si substrate 21.

Subsequently, for example, an Al film may be formed on the interlayerinsulating film 22A₁ with use of, for example, sputtering method orvacuum evaporation method, and then patterning may be performed with useof photolithography or etching to form the metallic film 22B₁ servingalso as the light shielding film 14. Next, the interlayer insulatingfilm 22A₂ is formed on the interlayer insulating film 22A₁ and themetallic film 22B₁, and then the metallic film 22B₂ is formed in apredetermined shape with use of similar method. Finally, the interlayerinsulating film 22A₃ is formed on the interlayer insulating film 22A₂and the metallic film 22B₂ to complete the wiring layer 22.

Note that the metallic film 22B₁ is formed with use of sputtering methodor vacuum evaporation method here; however, the method is not limitedthereto, and the metallic film 22B₁ may be formed with use of, forexample, plating method. FIG. 12 illustrates a sectional structure of animage sensor 1F in which the metallic film 22B₁ is formed with use ofplating method. When the metallic film 22B₁ of the wiring layer 22 inthe present embodiment is formed with use of plating method, thethickness of the metallic film 22B1 on the image plane phase differencepixel 2B becomes large as illustrated in FIG. 12.

Further, the wiring layer 22 in which the metallic film 22B has thetwo-layer structure has been described; however, this is not limitative,and the wiring layer 22 may have a multilayer wiring structure in whichthe metallic film 22B is formed of three or more layers.

FIG. 13 illustrates another example of an image sensor (an image sensor1G) in the present embodiment. In the image sensor 1G, the metallic film22B of the wiring layer 22 has three-layer structure (22B₁, 22B₂, and22B₃), and the light shielding films 14A and 14C covering the step part20A in the first embodiment and the like are separately formed of themetallic films 22B₁ and 22B₂, respectively.

Such a wiring layer 22 may be formed with use of the followingmanufacturing method, for example. First, for example, a SiO₂ film maybe formed on the Si substrate 21 provided with the step part 20A withuse of, for example, CVD method, and then the interlayer insulating film22A₁ may be formed by etching or polishing. Subsequently, for example,an Al film may be formed on a predetermined position on the interlayerinsulating film 22A₁ with use of, for example, sputtering method orvacuum evaporation method, and then patterning may be performed with useof photolithography or etching to form the metallic film 22B1 servingalso as the light shielding film 14.

Specifically, the metallic film 22B₁ is formed on a positioncorresponding to the light shielding film 14A covering the side wall 20Bof the step part 20A, a position corresponding to the light shieldingfilm 14B for pupil division between the image plane phase differencepixels 2B adjacent to each other, and a position corresponding to thenormal light shielding film 14C. Then, the interlayer insulating film22A₂ is formed on the interlayer insulating film 22A₁ and the metallicfilm 22B₁, and then the metallic film 22B₂ is formed in a predeterminedshape with use of similar method. Further, the interlayer insulatingfilm 22A₃ and the metallic film 22B₃ are formed. Finally, the interlayerinsulating film 22A₄ is formed on the interlayer insulating film 22A₂and the metallic film 22B₂ to complete the wiring layer 22.

In the image sensor 1G illustrated in FIG. 13, as described above, thelight shielding film 14 in the first embodiment and the like is formedof two layers, the metallic film 22B₁ and the metallic film 22B₂provided on different layers. Therefore, the metallic film 22B₁corresponding to the light shielding film 14A covering the side wall 20Bof the step part 20A is discontinuous with the metallic film 22B₂serving also as the light shielding film 14C provided on the imagepickup pixel 2A.

Note that, as illustrated in FIGS. 11 and 12, when the light shieldingfilm 14 in the first embodiment and the like is formed of one layer ofthe metallic film 22B₁ (in other words, formed at the same step), thelight shielding films 14A and 14C of the step part 20A are continuouslyformed. Therefore, high light shielding property is obtainable. On theother hand, when the light shielding film 14 is formed of two layers ofthe metallic film 22B₁ and the metallic film 22B₂ as illustrated in FIG.13, it is possible to form each of the interlayer insulating film 22A(22A₁, 22A₂, 22A₃, and 22A₄) and the metallic film 22B (22B₁, 226 ₂, and22B₃) of the wiring layer 22 with ease.

Moreover, the color filter 12 of the image plane phase difference pixel2B in the present embodiment may be preferably assigned with green (G)or white (W), similarly to the first embodiment; however, when lighthaving high quantity enters the image plane phase difference pixel 2B,the charge is easily saturated in the photodiode 23. At this time, inthe case of the surface irradiation type, excess charge is dischargedfrom a lower side of the Si substrate 21 (from the substrate 21 side).Accordingly, a lower part of the Si substrate 21 at a positioncorresponding to the image plane phase difference pixel 2B,specifically, a lower part of the photodiode 23 may be doped with p-typeimpurity with higher concentration to raise overflow barrier.

In this way, the present disclosure is applicable to the surfaceirradiation type image sensor without being limited to the backsideirradiation type image sensor, and it is possible to obtain effectsequivalent to those in the above-described first embodiment and the likeeven in the case of the surface irradiation type.

5. Third Embodiment

As a third embodiment, a backside irradiation type image sensor in whicha step part is provided between a first pixel and a second pixel, afirst light shielding section is provided on side walls of the steppart, and an inner lens is further provided is described as an example.

As described with reference to FIG. 7A, FIG. 7B, FIG. 8A, and FIG. 8B,for example, the pixel 2 illustrated in FIG. 3 may be designed in such amanner that incident light in the image pickup pixel 2A is condensednear the photodetection surface 20S and incident light in the imageplane phase difference pixel 2B is condensed at the same depth positionas that of the light shielding film 14B for pupil division. Accordingly,similarly to the image pickup pixel 2A, the image plane phase differencepixel 2B is also configured in such a manner that luminous fluxes ofsubstantially all of the incident light that have passed through theon-chip lens 11 are applied to the photodiode 23.

As described with reference to FIG. 7B and FIG. 8B, it is found fromcomparison between the characteristic diagram of FIG. 7A and thecharacteristic diagram of FIG. 8B that the photodetection efficiency ofthe image plane phase difference pixel 2B in which the photodetectionsurface 20S is disposed at the position deeper than that of the imagepickup pixel 2A is higher than the photodetection efficiency of theimage pickup pixel 2A, namely, the characteristics of pupil intensitydistribution of the image plane phase difference pixel 2B are sharperthan those of the image pickup pixel 2A. In other words, it becomespossible for the image plane phase difference pixel 2B of the imagesensor 1 in the present embodiment to generate the signal for phasedifference detection with accuracy higher than that of the image planephase difference pixel 102B of the image sensor 100 in the comparativeexample, in phase difference detection.

Moreover, in the present embodiment, providing the light shielding film14A on the side wall 20B of the step part 20A suppresses color mixingcaused by crosstalk of the oblique incident light between the pixelsadjacent to each other.

However, providing the photodetection surface 20S of the image planephase difference pixel 2B at a position deeper than the photodetectionsurface 20S of the image pickup pixel 2A may influence the image pickupcharacteristics of the image plane phase difference pixel 2B. Referringto FIG. 3 again, the image plane phase difference pixel 2B is larger incarved amount of the Si substrate 21 than the image pickup pixel 2A.Therefore, the photodiode 23 of the image plane phase difference pixel2B is formed to be smaller in size than the photodiode 23 of the imagepickup pixel 2A.

When the photodiode 23 is configured as described above, the imagepickup characteristics of the photodiode 23 of the image plane phasedifference pixel 2B may be deteriorated, for example, the number ofsaturation electrons of the photodiode 23 of the image plane phasedifference pixel 2B may become lower than that of the photodiode 23 ofthe image pickup pixel 2A.

Thus, as illustrated in FIG. 14, an inner lens is provided in the imageplane phase difference pixel 2B. FIG. 14 is a diagram illustrating astructure of the pixel 2 in the third embodiment. In FIG. 14, the wiringlayer 22 is not illustrated, and the structure of the light condensingsection 10 is illustrated in a simplified manner for description.

The image plane phase difference pixel 2B illustrated in FIG. 14 has aninner lens 17. The inner lens 17 is provided between the on-chip lens 11and the photodiode 23. Further, the inner lens 17 is provided in theimage plane phase difference pixel 2B, and is not provided in the imagepickup pixel 2A. For example, when a plurality of image plane phasedifference pixels 2B are provided continuously as illustrated in FIG. 5,the inner lens 17 may be used commonly to the plurality of image planephase difference pixels 2B.

When the inner lens 17 is provided as described above, light condensedby the on-chip lens 11 is further condensed by the inner lens 17 asillustrated in FIG. 14. With such a structure, it is possible to providethe photodetection surface 20S of the image plane phase difference pixel2B on an upper side (on the on-chip lens 11 side) as compared with thephotodetection surface 20S of the image plane phase difference pixel 2Bwithout the inner lens 17 illustrated in FIG. 3.

Specifically, it becomes possible to reduce the carved amount of the Sisubstrate 21 of the image plane phase difference pixel 2B as comparedwith the image plane phase difference pixel 2B without the inner lens 17illustrated in FIG. 3. As a result, it becomes possible to make thephotodiode 23 of the image plane phase difference pixel 2B larger thanthe photodiode 23 of the image plane phase difference pixel 2B withoutthe inner lens 17.

Therefore, it is possible to configure the image plane phase differencepixel 2B that suppresses deterioration of the image pickupcharacteristics caused by decrease of the saturation electron amount ofthe photodiode of the image plane phase difference pixel 2B.

In addition, basically, the image plane phase difference pixel 2Billustrated in FIG. 14 has a similar structure of the image plane phasedifference pixel 2B illustrated in FIG. 3 except that the inner lens 17is provided. Therefore, effects obtained by the image plane phasedifference pixel 2B illustrated in FIG. 3 are obtainable also by theimage plane phase difference pixel 2B illustrated in FIG. 14. In otherwords, for example, similarly to the image pickup pixel 2A, it ispossible to configure the image plane phase difference pixel 2B in sucha manner that the luminous fluxes of substantially all of the incidentlight that have passed through the on-chip lens 11 are applied to thephotodiode 23, and it is possible to generate a signal for phasedifference detection with higher accuracy.

FIG. 15 is a diagram illustrating a structure of the pixel 2 in a casewhere the inner lens 17 is provided in the image plane phase differencepixel 2B illustrated in FIG. 3.

In the image plane phase difference pixel 2B illustrated in FIG. 15, theinsulating film 15 that has a predetermined height of the lightshielding film 14B is provided between the light shielding films 14B,namely, on a part corresponding to the step part 20A. Incidentally,description is given for an example in which the insulating film 15 isprovided on a lower side and an upper side of the light shielding film14A. However, for example, as with the image plane phase differencepixel 2B illustrated in FIG. 3, the insulating film 15 may be providedon the lower side of the light shielding film 14A, and the planarizingfilm 13 may be provided on the upper side of the light shielding film14A.

As described above, examples of the material of the insulating film 15may include a silicon oxide film (SiO₂), a silicon nitride film (SiN),and a silicon oxynitride film (SiON). Examples of the material of theplanarizing film 13 may include a silicon oxynitride film (SiO₂), asilicon nitride film (SiN), and silicon oxynitride film (SiON). When thesame material is used for the insulating film 15 and the planarizingfilm 13, a film formed of the same material is formed on each of thelower side and the upper side of the light shielding film 14A asillustrated in FIG. 15.

Such difference depends on the manufacturing step and the material to beused. Here, first, description is given for an example in which a filmmade of the same material is formed on each of the lower side and theupper side of the light shielding film 14A, and description issuccessively given while the formed film is referred to as theinsulating film 15.

Incidentally, in this case, functionally, the film on the lower side ofthe light shielding film 14A has a function of preventing damage of theSi substrate 21 in processing of the light shielding film 14, and thefilm on the upper side has a function of planarizing the photodetectionsurface 20S of the photodetection section 20 and the lower surface ofthe inner lens 17.

The inner lens 17 is formed on the insulating film 15 formed between theinsulating films 14B. Examples of the material of the inner lens 17 mayinclude a silicon nitride film (SiN). Further, for example, examples ofthe material of the inner lens 17 may include a siloxane-based resin(refractive index 1.7) and a high refractive index resin such aspolyimide. Further, the above-described resin may contain metal oxidemicroparticles of, for example, titanium oxide, tantalum oxide, niobiumoxide, tungsten oxide, zirconium oxide, zinc oxide, indium oxide, andhafnium oxide to enhance refractive index.

The color filter 12 is formed on the inner lens 17. In this way, in theimage plane phase difference pixel 2B illustrated in FIG. 15, the colorfilter 12 is formed on the inner lens 17; however, a planarizing organicfilm 18 may be provided on the inner lens 17, and the color filter 12may be formed on the planarizing organic film 18, as illustrated in FIG.16.

In the image plane phase difference pixel 2B illustrated in FIG. 16, theplanarizing organic film 18 is formed between the inner lens 17 and thecolor filter 12. The planarizing organic film 18 may be provided belowthe color filter 12 as with the image plane phase difference pixel 2Billustrated in FIG. 16, or the inner lens 17 may be directly providedbelow the color filter 12 without providing the planarizing organic film18 as with the image plane phase difference pixel 2B illustrated in FIG.15.

Further, the inner lens 17 may not have a curved shape (an upward convexstructure) illustrated in FIG. 15 and FIG. 16 but may have a rectangularshape (a box shape) as illustrated in FIG. 17. An inner lens 17′illustrated in FIG. 17 has a rectangular sectional surface. Therectangular inner lens 17′ has a feature of condensing light in a pixelhaving a reduced size. Moreover, the rectangular inner lens 17′ iseasily manufactured as compared with the curved inner lens 17.

Here, although the curved inner lens 17 and the rectangular inner lens17′ have been described as examples, the inner lens may have othershapes.

Moreover, the example in which one inner lens is provided in a verticaldirection, namely, between the color filter 12 and the photodiode 23 hasbeen described here. However, the number of inner lens is not limited toone, and a plurality of inner lenses may be provided while beingoverlapped. In addition, when the plurality of inner lenses areprovided, inner lenses having shapes different from one another may becombined and used.

The inner lenses illustrated in FIG. 15 to FIG. 17 are each provided onthe photodiode 23 side as an example; however, a configuration in whichan inner lens 19 is provided on the color filter 12 side as illustratedin FIG. 18 may be employed.

The step part 20A of the image plane phase difference pixel 2Billustrated in FIG. 18 is filled with a planarizing organic film 18′. Inthe image plane phase difference pixel 2B, the S substrate 21 is carvedby an amount of the step part 20A as compared with the image pickuppixel 2A. Therefore, it is possible to form the planarizing organic film18′ such that a recess is formed, with use of the carving.

For example, depression may be formed in the image plane phasedifference pixel 2B by self-alignment, and the inner lens 19 may beformed in the depression. The inner lens 19 to be formed is an innerlens having a downward convex shape (having a curved shape on a downside) as illustrated in FIG. 18.

Note that, in the example illustrated in FIG. 18, the example in whichthe step part 20A of the image plane phase difference pixel 2B is filledwith the planarizing organic film 18′ is illustrated. However, asillustrated in FIG. 15 to FIG. 17, the step part 20A of the image planephase difference pixel 2B may be filled with the insulating film 15, orfilled with the insulating film 15 and the planarizing organic film 18.

<Manufacture of Image Pickup Device According to Third Embodiment>

Manufacture of the image sensor 1A including the image plane phasedifference pixel 2B that includes the inner lens described withreference to FIG. 14 to FIG. 18 is described with reference to FIG. 19to FIG. 21. Note that a case where the image sensor 1A including theimage plane phase difference pixel 2B illustrated in FIG. 16 ismanufactured is described as an example here.

At step S1 illustrated in FIG. 19, a mask 31 is formed on thephotodetection surface side of the backside irradiation type solid-stateimage pickup device. The mask 31 is formed at parts other than parts tobe the image plane phase difference pixels 2B. Then, the Si substrate 21corresponding to the image plane phase difference pixel 2B is etched.

In this etching, plasma etching and wet etching may be used.Incidentally, when wet etching of silicon is performed,nitrohydrofluoric acid or alkali may be preferably used, and in thiscase, a hard mask of an oxide film or a nitride film may be preferablyused.

At step S2, the mask 31 is peeled off after the etching of the Sisubstrate 21. In the case of a resist mask, ashing or sulfuricacid/hydrogen peroxide mixture is used, and in the case of a hard maskof an oxide film or a nitride film, hydrofluoric acid is used.

At step S3, each of the fixed charge film 24, the insulating film 15,and the light shielding film 14 is formed on the front surface of the Sisubstrate 21. The fixed charge film 24 may be formed as anantireflection film. For example, hafnium oxide (HfO₂), aluminum oxide(Al₂O₃), zirconium oxide (ZrO₂) film, tantalum oxide (Ta₂O₅), ortitanium oxide (TiO₂), or a stacked-layer film thereof may be used forthe antireflection film (the fixed charge film 24).

After the fixed charge film 24 is formed, the insulating film 15 isformed. The insulating film 15 also functions as an interlayer filmprovided between the fixed charge film 24 and the light shielding film14. For example, a silicon oxide film (SiO₂), a silicon nitride film(SiN), or a silicon oxynitride film (SiON) may be used for theinsulating film 15.

As the method of forming the insulating film 15, CVD method and ALDmethod are used; however, a formation method excellent in side coveragemay be preferably selected in order to form the insulating film 15 onthe side wall of the step part 20A of the image plane phase differencepixel 2B.

After the insulating film 15 is formed, the light shielding film 14 isformed. For example, tungsten (W), aluminum (Al), an alloy of Al andcopper (Cu) may be used for the light shielding film 14. As the methodof forming the insulating film 14, PDV method, CVD method, and ALDmethod are used; however, a formation method excellent in side coveragemay be preferably selected in order to form the light shielding film 14on the side wall of the step part 20A of the image plane phasedifference pixel 2B.

At step S5 illustrated in FIG. 20, lithography to remove unnecessarypart of the light shielding film 14 to process the light shielding film14 is performed. Since the step part 20A exists in the image plane phasedifference pixel 2B, an exposure method in which focus is adjusted onboth of the bottom surface and the top surface of the step part 20A maybe preferably used.

At the step S5, the light shielding film 14 is processed by dry etching.For example, in the processing, resist is peeled off by ashing after dryetching to form the light shielding film 14A, the light shielding film14B, and the light shielding film 14C.

At step S6, a part of the insulating film 15 is formed. The lightshielding film 15 that is charged in the step part 20A of the imageplane phase difference pixel 2B to allow the inner lens to be formed onthe planarized film is formed on the already formed insulating film 15.

In the formation of the insulating film 15 at the step S6, high densityplasma (HDP) method may be preferably used to form the insulating film15 because the step part 20A of the image plane phase difference pixel2B may be preferably planarized at subsequent step S7.

As illustrated in FIG. 20, the insulating film 15 formed at the step S6is formed in a shape including a recess on a part of the image planephase difference pixel 2B since the step part 20A exists in the imageplane phase difference pixel 2B.

At the step S7, chemical mechanical polishing (CMP) is used to planarizethe oxide film. As illustrated in FIG. 20, the oxide film is polished upto the upper surface of the light shielding film 14C, and as a result,the oxide film is planarized.

At step S8, the surface other than the step part 20A of the image planephase difference pixel 2B is covered with a resist mask 33, and etchback is performed by dry etching. As a result, a space (a space wherethe inner lens is formed) configuring light condensing structure issecured at the step part 20A of the image plane phase difference pixel2B.

In the case of the configuration in which the step part 20A is filledwith the planarizing organic film 18′ as illustrated in FIG. 18, theplanarizing organic film 18′ is first formed at the step S6 out of thestep S6 to step S8. The planarizing organic film 18′ is also formed bythe method same as the film formation of the insulating film 15described above.

Further, the planarizing organic film 18′ is also formed in a shape inwhich a recess is generated on a part of the image plane phasedifference pixel 2B because the step part 20A exists in the image planephase difference pixel 2B as illustrated in FIG. 20. It is possible toform the inner lens 19 (FIG. 18) with use of the recess.

Specifically, for example, the planarizing organic film 18′ may beformed to have the recess with a predetermined depth at the step S6, andpolishing may be performed at the step S7 while remaining the spacewhere the inner lens 19 (FIG. 18) is to be formed. As a result, it ispossible to form the space where the inner lens 19 is to be formed. Inthis case, the step S8 may be omitted.

Moreover, at the step S8, it is also possible to form such a recesswhere the inner lens 19 is to be formed. The position, the size, thecurvature, the depth, etc. of the recess where the inner lens 19 is tobe formed may be arbitrary controlled by an opening of the resist mask,etching time, etc.

The description is returned to manufacture with reference to FIG. 20.When the space where the inner lens is to be formed is formed at thestep S8, the processing proceeds to step S9 illustrated in FIG. 21.

At the step S9, a high refractive index material, for example, a siliconnitride (SiN) film 34 may be formed. The silicon nitride film 34 to beformed becomes a material of the inner lens. Although the siliconnitride film 34 is described as an example here, a film of a materialmatched with the inner lens to be formed is formed at the step S9.

At step S10, lithography of the inner lens is performed on the step part20A of the image plane phase difference pixel 2B. A mask 35 matched withthe desired shape of the inner lens is formed.

At step S11, dry etching is performed to form the inner lens 17 on thestep part 20A of the image plane phase difference pixel 2B.

When the mask 35 is formed in a curved shape as illustrated in FIG. 21at the step S10, the curved inner lens 17 illustrated in FIG. 15 andFIG. 16 is formed. When the mask 35 is formed in a rectangular shape atthe step 10 although not illustrated, the rectangular inner lens 17′illustrated in FIG. 17 is formed.

In this way, the mask 35 matched with the shape of the inner lens to beformed is formed and the etching is performed. As a result, the curvedinner lens or the rectangular inner lens is formed.

At step S12, the color filter 12 is formed on the formed inner lens 17and the formed insulating film 15, and the on-chip lens 11 is formed onthe color filter 12. In this way, the image sensor 1A including theimage plane phase difference pixel 2B illustrated in FIG. 15 is formed.

When the image sensor 1A including the image plane phase differencepixel 2B illustrated in FIG. 16 or FIG. 17 is formed, after theplanarizing organic film 18 is formed on the inner lens 17 (or the innerlens 17′) at the step S12, the color filter 12 is formed and the on-chiplens 11 is then formed.

In this way, the image sensor 1A including the image plane phasedifference pixel 2B that includes the inner lens is manufactured.

When the inner lens is provided on such an image plane phase differencepixel 2B, it is possible to suppress deterioration of the image pickupcharacteristics, for example, reduction of saturation electron amount ofthe image plane phase difference pixel 2B without impairing focusdetection accuracy of the image plane phase difference pixel 2B.

Further, when the image plane phase difference pixel 2B is used also asa pixel for image pickup, it is possible to configure the image sensor1A that is capable of simply correcting an image with less difference ofthe image pickup characteristics from those of the image pickup pixel2B.

6. Application Examples

Hereinafter, application examples of the image sensors 1 described inthe above-described first, second, and third embodiments are described.All of the image sensors 1 in the above-described embodiments areapplicable to electronic apparatuses in various fields. Here, asexamples, an image pickup apparatus (a camera), an endoscope camera, anda vision chip (an artificial retina) are described.

Application Example 1

FIG. 22 is a functional block diagram illustrating an entireconfiguration of the image pickup apparatus (an image pickup apparatus300). The image pickup apparatus 300 may be, for example, a digitalstill camera or a digital video camera, and may include an opticalsystem 310, a shutter device 320, the image sensor 1 (for example, theimage sensor 1A), a signal processing circuit 330 (an image processingcircuit 340 and an AF processing circuit 350), a drive circuit 360, anda control section 370.

The optical system 310 include one or a plurality of image pickup lenseseach forming an image of picked-up image light (incident light) from anobject on an image pickup surface of the image sensor 1. The shutterdevice 320 controls a light application period (an exposure period) anda light shielding period with respect to the image sensor 1. The drivecircuit 360 performs open-close driving of the shutter device 320, anddrives exposure operation and signal readout operation in the imagesensor 1.

The signal processing circuit 330 performs predetermined signalprocessing, for example, various correction processing such as demosaicprocessing and white balance adjustment processing on output signals(SG1 and SG2) from the image sensor 1. The control section 370 may beconfigured of, for example, a microcomputer, and controls the shutterdriving operation and the image sensor driving operation in the drivecircuit 360 and controls the signal processing operation in the signalprocessing circuit 330.

In the image pickup apparatus 300, when incident light is detected bythe image sensor 1 through the optical system 310 and the shutter unit320, signal charge based on the amount of the detected light isaccumulated in the image sensor 1. The signal charge accumulated in eachpixel 2 of the image sensor 1 (the electric signal SG1 obtained from theimage pickup pixel 2A and the electric signal SG2 obtained from theimage plane phase difference pixel 2B) is read out by the drive circuit360, and the read electric signals SG1 and SG2 are output to the imageprocessing circuit 340 and the AF processing circuit 350 of the signalprocessing circuit 330.

The output signals output from the image sensor 1 are subjected topredetermined signal processing by the signal processing circuit 330,and the processed signal is output to outside (a monitor, or the like)as a picture signal Dout, or retained in a storage section (a storagemedium) such as a unillustrated memory.

Application Example 2

FIG. 23 is a functional block diagram illustrating an entireconfiguration of the endoscope camera (a capsule endoscope camera 400A)according to an application example 2. The capsule endoscope camera 400Aincludes an optical system 410, a shutter device 420, the image sensor1, a drive circuit 440, a signal processing circuit 430, a datatransmission section 450, a drive battery 460, and an attitude(direction and angle) sensing gyro circuit 470.

Among them, the optical system 410, the shutter device 420, the drivecircuit 330, and the signal processing circuit 430 have functionssimilar to those of the optical system 310, the shutter device 320, thedrive circuit 360, and the signal processing circuit 330 described inthe above-described image pickup apparatus 300, respectively. Note thatthe optical system 410 may be desirably adapted to pick up an image in aplurality of azimuth directions (for example, all-around) infour-dimensional space, and may be configured of one or a plurality oflenses. Incidentally, in this example, a picture signal D1 subjected tothe signal processing by the signal processing circuit 430 and anattitude sensing signal D2 output from the gyro circuit 470 aretransmitted to an external apparatus through the data transmissionsection 450 via wireless communication.

Note that the endoscope camera to which the image sensor in any of theabove-described embodiments is applicable is not limited to theabove-described capsule endoscope camera, and for example, may be aninsertion endoscope camera (an insertion endoscope camera 400B) asillustrated in FIG. 24.

The insertion endoscope camera 400B includes the optical system 410, theshutter device 420, the image sensor 1, the drive circuit 440, thesignal processing circuit 430, and the data transmission section 450,similar to a part of the configuration of the above-described capsuleendoscope camera 400A. Incidentally, the insertion endoscope camera 400Bfurther includes an arm 480 a storable in the device and a drive section480 configured to drive the arm 480 a. Such an insertion endoscopecamera 400B is connected to a cable 490 that includes a wiring 490Atransmitting an arm control signal CTL to the drive section 480 and awiring 490B transmitting a picture signal Dout based on the picked-upimage.

Application Example 3

FIG. 25 is a functional block diagram illustrating an entireconfiguration of the vision chip (a vision chip 500) according to anapplication example 3. The vision chip 500 is an artificial retinaburied in a part of an inner wall (a retina E2 having visual nerve) ofan eyeball E1 for use. The vision chip 500 may be buried in a part ofany of a ganglion cell C1, a horizontal cell C2, and a visual cell C3 ofthe retina E2, and may include, for example, the image sensor 1, asignal processing circuit 510, and a stimulation electrode section 520.

Thus, the vision chip 500 obtains the electric signal based on incidentlight to the eye by the image sensor 1, processes the electric signal bythe signal processing circuit 510, and supplies a predetermined controlsignal to the stimulation electrode section 520. The stimulationelectrode section 520 has a function of applying stimulus (the electricsignal) to the visual nerve in response to the input control signal.

Hereinbefore, although the disclosure has been described with referenceto the first, second, and third embodiments, the disclosure is notlimited to the above-described embodiments and the like, and variousmodifications may be made. Another optical functional layer may beprovided between the on-chip lens and the photodetection section.Moreover, a multiple lens structure in which a lens (a so-called innerlens) is further provided below the on-chip lens 11, specificallybetween the on-chip lens 11 and the photodetection section 20 may beemployed.

Note that the technology may be configured as follows.

(1) An image pickup device including

a first pixel and a second pixel each including a photodetection sectionand a light condensing section, the photodetection section including aphotoelectric conversion element, the light condensing sectioncondensing incident light toward the photodetection section, the firstpixel and the second pixel being adjacent to each other and each havinga step part on a photodetection surface of the photodetection section,wherein

at least a part of a wall surface of the step part is covered with afirst light shielding section.

(2) The image pickup device according to (1), wherein

the light condensing section includes a lens as an optical functionallayer, and

the lens of the light condensing section of the first pixel has a shapesame as the lens of the light condensing section of the second pixel.

(3) The image pickup device according to (2), wherein

the lens of the light condensing section of the first pixel is opposedto the photodetection section of the first pixel, and

the lens of the light condensing section of the second pixel is opposedto the photodetection section of the second pixel.

(4) The image pickup device according to any one of (1) to (3), whereinthe wall surface of the step part is perpendicular.

(5) The image pickup device according to any one of (1) to (4), whereinthe second pixel includes a second light shielding section that shieldsa part of the photodetection surface, between the photodetection sectionand the light condensing section.

(6) The image pickup device according to any one of (1) to (5), whereinthe first pixel and the second pixel includes a third light shieldingsection between the first pixel and the second pixel adjacent to eachother.

(7) The image pickup device according to (6), wherein the first lightshielding section, the second light shielding section, and the thirdlight shielding section are formed of a same material.

(8) The image pickup device according to any one of (1) to (7), whereinthe incident light of the first pixel is condensed near thephotodetection surface of the photodetection section.

(9) The image pickup device according to any one of (1) to (8), whereinthe incident light of the second pixel is condensed at a depth positionsame as a depth position of the second light shielding section.

(10) The image pickup device according to any one of (1) to (9), whereinthe step part is filled with an organic film.

(11) The image pickup device according to (10), wherein the organic filmis formed of one of a polyimide resin, an acrylic resin, a styreneresin, and an epoxy resin.

(12) The image pickup device according to any one of (1) to (11),wherein the first pixel and the second pixel each include a fixed chargefilm between the photodetection section and the light condensingsection.

(13) The image pickup device according to any one of (1) to (12),wherein

the first pixel and the second pixel include a groove between the firstpixel and the second pixel adjacent to each other, and

the fixed charge film is provided along wall surfaces and a bottomsurface of the groove.

(14) The image pickup device according to (13), wherein the groove isfilled with an insulating material.

(15) The image pickup device according to (13), wherein the groove isfilled with an insulating material and one of the first light shieldingsection, the second light shielding section, and the third lightshielding section.

(16) The image pickup device according to any one of (1) to (15),wherein

a drive section including a wiring layer is provided between the lightcondensing section and the photodetection section, and

the wiring layer also serves as the first light shielding section, thesecond light shielding section, and the third light shielding section.

(17) The image pickup device according to any one of (1) to (16),wherein

the light condensing section includes a color filter of red, green,blue, or while, and

the light condensing section of the second pixel includes a color filterof green or white.

(18) The image pickup device according to any one of (1) to (17),wherein an inner lens is provided on the step part.

(19) The image pickup device according to (18), wherein the inner lensis an inner lens having an upward convex structure or a downward convexstructure, or a rectangular inner lens.

(20) An image pickup apparatus including an image pickup device, theimage pickup device including

a first pixel and a second pixel each including a photodetection sectionand a light condensing section, the photodetection section including aphotoelectric conversion element, the light condensing sectioncondensing incident light toward the photodetection section, the firstpixel and the second pixel being adjacent to each other and each havinga step part on a photodetection surface of the photodetection section,wherein

at least a part of a wall surface of the step part is covered with afirst light shielding section.

This application is based upon and claims the benefit of priority of theJapanese Patent Application No. 2013-73054, filed on Mar. 29, 2013, andthe Japanese Patent Application No. 2014-49049, filed on Mar. 12, 2014,both filed with the Japan Patent Office, the entire contents of theseapplications are incorporated herein by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. An imaging device comprising: a substrate;a first photoelectric conversion region disposed in the substrate; asecond photoelectric conversion region disposed in the substrate, thesecond photoelectric conversion region being adjacent to the firstphotoelectric conversion region; a third photoelectric conversion regiondisposed in the substrate, the third photoelectric conversion beingadjacent to the second photoelectric conversion region; a first trenchdisposed between the first photoelectric conversion region and thesecond photoelectric conversion region; and a second trench disposedbetween the second photoelectric conversion region and the thirdphotoelectric conversion region, wherein an area of the firstphotoelectric conversion region is larger than an area of the secondphotoelectric conversion region in a cross-sectional view, wherein, inthe cross-sectional view, the first trench extends a first distancealong a first sidewall of the first photoelectric conversion region,wherein the first distance is taken along the first side wall from afirst light receiving surface of the first photoelectric conversionregion to an end of the first trench, wherein, in the cross-sectionalview, the second trench extends a second distance along a secondsidewall of the second photoelectric conversion region, wherein thesecond distance is taken along the second sidewall from a second lightreceiving surface of the second photoelectric conversion region to anend of the second trench, and wherein the first distance is greater thanthe second distance.
 2. The imaging device of claim 1, wherein the firsttrench and the second trench are filled with at least one firstinsulating material.
 3. The imaging device of claim 2, wherein the atleast one first insulating material includes a first insulating materialand a second insulating material.
 4. The imaging device of claim 3,wherein the first insulating material includes silicon oxide.
 5. Theimaging device of 24, wherein the second insulating material includeshafnium oxide.
 6. The imaging device of claim 5, wherein the hafniumoxide surrounds the silicon oxide in the first trench and the secondtrench.
 7. The imaging device of claim 2, further comprising: at leastone second insulating material, wherein the at least one firstinsulating material is disposed on the first light receiving surface andthe second light receiving surface, and wherein the at least one secondinsulating material is disposed on the at least one first insulatingmaterial.
 8. An imaging device comprising: a substrate; a firstphotoelectric conversion region disposed in the substrate; a secondphotoelectric conversion region disposed in the substrate, the secondphotoelectric conversion region being adjacent to the firstphotoelectric conversion region; a third photoelectric conversion regiondisposed in the substrate, the third photoelectric conversion beingadjacent to the second photoelectric conversion region; a first pixelseparation region disposed between the first photoelectric conversionregion and the second photoelectric conversion region; and a secondpixel separation region disposed between the second photoelectricconversion region and the third photoelectric conversion region, whereinan area of the first photoelectric conversion region is larger than anarea of the second photoelectric conversion region in a cross-sectionalview, wherein, in the cross-sectional view, the first pixel separationregion extends a first distance along a first sidewall of the firstphotoelectric conversion region, wherein the first distance is takenalong the first sidewall from a first light receiving surface of thefirst photoelectric conversion region to an end of the first pixelseparation region, wherein, in the cross-sectional view, the secondpixel separation region extends a second distance along a secondsidewall of the second photoelectric conversion region, wherein thesecond distance is taken along the second sidewall from a second lightreceiving surface of the second photoelectric conversion region to anend of the second pixel separation region, and wherein the firstdistance is greater than the second distance.
 9. The imaging device ofclaim 8, wherein the first pixel separation region and the second pixelseparation region are filled with at least one first insulatingmaterial.
 10. The imaging device of claim 9, wherein the at least onefirst insulating material includes a first insulating material and asecond insulating material.
 11. The imaging device of claim 10, whereinthe first insulating material includes silicon oxide.
 12. The imagingdevice of 11, wherein the second insulating material includes hafniumoxide.
 13. The imaging device of claim 12, wherein the hafnium oxidesurrounds the silicon oxide in the first pixel separation region and thesecond pixel separation region.
 14. The imaging device of claim 9,further comprising: at least one second insulating material, wherein theat least one first insulating material is disposed on the first lightreceiving surface and the second light receiving surface, and whereinthe at least one second insulating material is disposed on the at leastone first insulating material.